The aim of this proposal is to help support an international symposium on "Chloride Signaling" to be held September 3-7, 2003, at the Marine Biological Laboratory in Woods Hole, Massachusetts. This meeting will be the 57th Annual Symposium of the Society of General Physiologists (SGP). The major, if not sole, purpose of the SGP is to host a symposium each year on a different subject. The topic of this meeting is especially timely and compelling. Anion channels in general have received less attention than cation channels, partly because their functions and pathophysiology was not as evident and because the available methodology was not powerful enough to crack them. Recently it has become clear that CI channels play very important roles in fundamental physiological and cell biological processes in ways that were not anticipated. Diseases due to CI channel defects are rapidly being discovered. This year the crystal structure of the first CI channel was published, which is certain to provide new and exciting insights into CI channel permeation. The symposium is titled "Chloride Signaling" rather than "Chloride Channels" because of the recent realization that cytosolic CI is dynamic and may have direct actions on the function of some proteins and because the regulation of intracellular CI depends on a variety of other active transport proteins. The hope is that this symposium will be formative in identifying important directions for research in the biology of chloride. The speakers have been selected to represent the leaders in chloride signaling around the world. The high-profile character of the subject makes us confident of high attendance (approximately 300 participants). Our publicity for the meeting will encourage participation from a wide sweep of scientists at all career levels-from structural biologists exploring the mechanisms of anion permeation and anion binding to proteins, to cell biologists interested in the roles of chloride in membrane trafficking, neuroscientists interested in the signaling of chloride channels, transport physiologists involved in ion homeostasis, and geneticists interested in channelopathies